The present invention relates to a computer system, and more particularly to a computer system provided with a storage device subsystem having both an interface compatible to a count-key data format and an interface compatible to a fixed length block format.
So-called down sizing which conducts applications which have heretofore been conducted in a main frame by using a so-called open system such as a personal computer or a workstation has recently been becoming popular. A large volume of information is stored in the main frame by the applications conducted heretofore and there is a big demand to access the information stored in the main frame from the open system. In the past, as for the sharing or file transformation of files between different operating systems, a technique to access a file in the MS-DOS operating system which is a personal computer operating system of the Microsoft Inc., USA, from the UNIX operating system on a workstation (operating system licensed by the X/Open Company Ltd., has been known.
Generally, in a computer system, information is stored in a storage device such as a disk storage. The main frame traditionally desired to use the disk access in the count-key-data format while the open system desires to use the disk access in the fixed length block format. Thus, the information used on the disk used in the main frame cannot be directly used from the open system. As techniques to access the information on the disk used in the main frame from the open system, a distributed database and a technique to utilize a file transfer have been known but such techniques have drawbacks in that they impose a heavy workload to a network and need modification of existing application programs.